Psoas mass index at the level of the third lumbar vertebra on computed tomography is a prognostic predictor for metastatic castration-sensitive prostate cancer.

Abstract

Computed tomography-defined low skeletal muscle mass is associated with oncological outcomes in patients with prostate cancer. However, its association with the outcomes of hormone-treated metastatic castration-sensitive prostate cancer remains unclear. We aimed to determine the association between metastatic castration-sensitive prostate cancer and psoas muscle parameters. We retrospectively reviewed 121 patients with N1 and/or M1 metastatic castration-sensitive prostate cancer who underwent primary androgen deprivation therapy between 2005 and 2021, either by administration of luteinizing hormone-releasing hormone agonist/antagonist or by surgical castration accompanied by bicalutamide, a first-generation antiandrogen. Before treatment administration, the psoas muscle index at the level of the third lumbar vertebra (psoas muscle area [cm2]/height2 [m2]) and the mean Hounsfield units of the psoas muscle were evaluated using non-contrast computed tomography and in relation to oncological outcomes. The median follow-up was 56.9months. Furthermore, during follow-up, 82 (67.7%) and 53 (43.8%) patients progressed to castration-resistant prostate cancer and died, respectively. Multivariate analysis of castration-resistant prostate cancer-free survival and overall survival showed significant differences in the Gleason score, clinical N-stage, and psoas muscle index (median cutoff: 3.044 cm2/m2). Pretreatment psoas muscle index is an independent predictor of poor castration-resistant prostate cancer-free survival and overall survival in patients with N1 and/or M1 metastatic castration-sensitive prostate cancer.